Apparatus for controlling the level of finely divided material within containers



March 31, 1942; c. NESS ETAL APPARATUS FOR CONTROLLING THE LEVEL OF FINELY DIVIDED MATERIAL WITHIN A CONTAINER Filed Oct. 12, 1938 3 Sheets-Sheet 1 INVENTORS CHARLES NESS HUGO V. KOJOLA GUY A. DUNN ATTO R N EY 3 Sheets-Sheet 2 C. NESS ET AL DIVIDED MATERIAL WITHIN A CONTAINER Filed Oct. 12, 1938 ATTORNEY March 31, 1942.

APPARATUS FOR'CONTROLLING THE LEVEL OF FINELY March 31, 1942. c. NEss ET AL APPARATUS FOR CONTROLLING THE LEVEL OF FINELY DIVIDED MATERIAL WITHIN A CONTAINER 1 3 Sheets-Sheet 5 Filed Oct. 12, 1938 IENTORS CHARLES N ESS HUGO v. KOJOLA GUY A. DUNN I RNE -Fatenteci Mar. 31, 1342 oNirEo sTArEs PATENT APPARATUS FOR CONTROLLING THE LEVEL OF FINELY DIVIDED MATERIAL WITHIN CONTAINERS Charles Ness, Indianapolis, Hugo V.

Whiting, and Guy A. Dunn, Beech Kojola, Grove, Ind.,

assignors to The Prest-O-Lite Company, Inc., a corporation of New York Application October 12, 1938, Serial No. 234,546

(Cl. 2141' l) 14 Claims.

- 9, moving body of calcium carbide is agitated and an amount of water is added thereto which is necessary to react the carbide completely and come apparent from the following description and accompanying drawings, in which:

Fig. 1 is a vertical sectional view of a hopper and a conveyor for removing lime therefrom, and

also an additional amount which by being vaporized reduces the temperature of the reaction mixture and so avoids a dangerous rise of temperature within the generator. In sucha process, the lime hydrate resulting from the reaction of calcium carbide and water is produced in substantially a dry form, and is continuously discharged from the generating zone into a container or hopper. It is desirable to maintain within the hopper a predetermined level of finely divided lime to act as a seal in order to prevent the outflow of acetylene or inflow of air, which otherwise would form an explosive mixture, either in the generating room or in the generator itself. A screw conveyor, or similar means, is usually utilized in removing the dry lime hydrate from the lime hopper, and it is desirable to so control the operation of the removing means that the removing means will be started in operation when the lime within the hopper reaches an upper predetermined level and will be stopped when the lime within the hopper reaches a lower predetermined level.

Among the objects of this invention are to provide apparatus for controlling the level of finely divided material in a container or hopper in accordance with the resistance of the material to a moving element within the hopper: to provide apparatus for controlling the removal of finely divided material from a container or hopper in accordance with the level therein; to provide such apparatus which will operate auto-' matically; to provide such apparatus which will function effectively and efiiciently irrespective of the rate at which finely divided material is fed into the container or hopper; to provide such apparatus which is simple and effective in operation; and to provide a novel stufling box for sealing shafts entering the container or hopper. Other objects and the novel features will beapparatus constructed in accordance with this invention for controlling the discharge of such.

lime;

Fig. 2 is an enlarged horizontal sectional view taken along the line 22 of Fig. 1;

Fig. 3 is a vertical sectional view of a lime hopper and conveyor similar to Fig. 1, illustratiznig a1. modification of the control apparatus of Fig. 4 is an enlarged horizontal sectional view taken along the line 4-4 of Fig. 3;

Fig. 5 is a diagrammaticplan of an electrical circuit of the control apparatus of Fig. 3;

Fig. 6 is a partial vertical sectional view of a lime hopper and a modification of the control apparatus of Fig. 3;

Fig. 7 is a vertical sectional view, partially diagrammatic, of a lime hopper and control apparatus. forming another embodiment of this invention;

Fig. 8 is a perspective -view of the coupling forming a part of the apparatus of Fig. 7, the coupling being disassembled for clarity of illustration;

Fig. 9 is anenlarged vertical sectional view of a stufiing box forming a part of the apparatus of Fig. 7;

Fig. 10 is a diagrammatic view of electrical control apparatus forming a modification of the apparatus of'Fig. 7; and Fig. 11 is a diagrammatic view. of electrical control apparatus forming a second modification of the apparatus of Fig. 7, Y

'As illustrated more particularly in Fig. 1, Fig.

3, and Fig. '7, the substantially dry lime hydrate v j passes from the generating chamber of an acetylene generator G into a lime hopper H or H,

from which it is removed by a screw conveyor C driven by a motor M. The conveyor 0 preferably is adapted to remove the lime at a rate in excess of the rate at which lime passes into the hopper, and the motor'M is preferably started when the lime reaches an upper level U, and stopped when the lime has been removed down to a lower level L. With the depth of lime withveyor C, or similar means for removing lime from in the hopper at all times at or above the lower the hopper, one or more movable elements are moved within the hopper through a predetermined preferably circular path or a path having predetermined upper and lower limits coinciding substantially with the upper and lower levels of the material in the hopper. The movable elements are preferably rotating paddles, and a suitable control means or mechanism for the motor M and conveyor C is associated therewith in such a manner that the resistance afforded to the movement of these elements by the material in the hopper will effect automatic operation of the lime removal means. In general, each movable element in the first embodiment, illustrated in Figs. 1-6, comprises a paddle or arm driven from a motor M, and changes in the resistance of lime to movement of this paddle cause a change in the angular relationship between the paddle and the shaft by which it is driven. In

the second embodiment, illustrated in Figs. 7-11,

a paddle or stirrer is continuously rotated within the lime hopper H by a motor M", and changes in resistance of lime to movement of the stirrer automatically control the motor driving the conveyor C. Force imposing means, such as weights or resilient means, are provided to resist displacement of the paddles or stirrers from their normal position due to resistance of the material in the container.

Referring more particularly to the embodiment of the invention illustrated in Figs. 1 and 2, finely divided and pulverous dry lime hydrate passes from the generating zone of the acetylene generator G into the lime hopper H through an outlet opening 26 controlled by a plate valve 2 I. The plate valve 2| is operated by a rod 22 having a handle 23 outside the hopper, the rod 22 passing through a stuffing box 24 in the upper wall of the hopper. As lime accumulates in the hopper H, it is removed through an outlet 25 in the lower end thereof by a helicoid screw 26 in the.

conveyor-C, the screw 26 being attached to a shaft 21 journalled in bearings 28 and rotated by the motor M through an integral speed reducer R. From an outlet 29 of the conveyor C, the lime may be deposited in a bin or other suitable stor-.

age means pending subsequent disposal.

A hollow shaft assembly A, which is rotated in.

cordance with the level of lime within the hopper. The paddle 30 is formed integrally with a stub shaft 32 which is journalled in a sleeve 33 offset from the center of a cylindrical housing 34. The lower end of the push rod 3| is slotted, and is provided with a pin 35, the pin cooperating with a forked yoke 36 secured to stub shaft 32 within housing 34. The forked outer end of yoke 36 extends into the slot in push rod 3| and pin is disposed between the forked ends of yoke 36, these forked ends moving rod 3| by contact with pin 35. The assembly A also includes a hollow shaft 31 to which housing 34 is secured and through which push rod 3| passes, and the rise or fall of lime within the hopper will cause a change in the angular relationship between paddle 30 and shaft 31,' thereby effecting a corresponding change in the position of push The housing 34 is filled with a lubricating medium, such as oil, which also permeates between push rod 3| and hollow shaft 31 to lubricate the same, and also serves as a sealing medium. A

packing gland 38 secured to sleeve 33 and a packing gland 39 at the upper end of hollow shaft 31 retain the lubricant within the assembly.

A disk 4| which rotates therewith is secured to the upper end of push rod 3|, and is adapted to move one end of a lever 42 upwardly and downwardly in accordance with the movement of the push rod. The other end of lever 42 is connected by a cable 43 with an operating arm 44 of a snapaction switch 45 which controls the motor M.

A weight 46 insures a continuous tension on cable 43, while weight 41 will cause the operating arm 44 to drop and thereby shut off the motor M should arm 44 become disconnected from cable 43 and weight 46. In addition, weights 48 carried by the upper end of push rod 3| tend to force the push rod downwardly at all times.

Due to its rotation, paddle 30 will always ride upon the top of the body of accumulated lime within the hopper, and when the lime has risen to the upper level U, paddle 30 will have been moved upwardly from its normal downwardly extending position and will have pushed rod 3| a sufficient distance upwardly to rock lever 42 and thereby exert a pull on cable 43; this will cause switch 45 to snap closed, thus starting the motor M. When the lime within the hopper has fallen to the lower level L, paddle 30 (moving downwardly with the lime) will cause rod 3| to be lowered, causing switch 45 to snap open, thus stopping the motor M and conveyor C. The removal of lime from the hopper H will continue in the same manner, the level of lime within the hopper being automatically maintained between predetermined lower and upper levels.

For starting the motor M manually if desired, a hand .pull ring 49 is connected to the end of lever 42 by a suitable cable.

The assembly A is rotated at its relatively slow speed by a motor M provided with an integral speed reducer R connected to one end of a shaft 5|. A bevel pinion 52 is attached to the other end of shaft 5 I. and bevel pinion 52 in turn drives a bevel gear 53 secured to the upper end of hollow shaft 31. shaft 5| are journalled in suitable bearings in a bracket 54, and a stuffing box 55 seals shaft 31 where it passes through the hopper H. g

The assembly A also includes a lower shaft 51, resting on a thrust bearing 58 and journalled in a sleeve bearing 59 mounted in a well 60 at the bottom of the hopper. A U-shaped scraper or sweep-frame 6| removes any incrustation of lime from the walls and bottom of the hopper, being secured at its lower end to shaft 51 by an inverted collar 62, which prevents entry of lime into well 60 and bearings 58 and 59. The scraper 6| at its upper end is secured to hollow shaft 31 by arms 63 attached to shaft 31 adjacent housing 34.

To prevent possible ignition of any air-acetylene mixture which might be present in the generator room, all electrical apparatus is preferably disposed outside the generator room, the conveyor C passing through a wall W of the room and an air-tight fitting 65 being provided at the wall for sealing purposes. The motor M is mounted on a platform 66 attached to the wall W outside the generator room, and switch 45 is also mounted outside the generator room. One end of shaft 5| is journalled in a bearing 61 mounted on platform 66, and shaft 5| passes through an air-tight housing 68 mounted in wall W, while cable 43 passes through a pipe 68,

Hollow shaft 31 and one end of mounted in the wall and provided with a stumng box 70.

In the embodiment of the invention illustrated in Figs. 3-5, the. acetylene generator G, hopper H, and conveyor C are substantially identical-with those illustrated in Figs. 1 and 2. A. shaft as sembly A, which includes a hollow shaft 31' and scraper 6i, is rotated at a relatively slow speed in the direction of arrow B, as before, by a suitable motor through pinion 52 attached to shaft 58 and bevel gear 53 attached to shaft 37, shafts 3'! and 5! being journalled in bracket 54. The assembly A also includes an upper paddle l5 and a lower paddle l6, respectively responsive to the upper and lower lime levels within the hopper. Disposed within hollow shaft 91' are a hollow push rod ll and a solid push rod I8, the hollow rod Tl being actuated by upper paddle through a cam 59, and the rod 78 being actuated by lower paddle 19 through a cam 00. Cam I9 is disposed within an upper housing 8I while cam 80 is disposed within a lower housing 82. Upper paddle l5 and cam 19 are keyed to opposite ends of a vertical stub shaft 843, and lower paddle I6 and cam 90 are keyed to opposite ends of a stub shaft 85, stub shafts 8E and 85 being journalled in upper and lower housings 8! and 02, respectively. Cams l9 and 89 are substantially identical in shape and size, except that upper cam I9 is provided with an arcuate slot 86, as in Fig. 4, through which solid push rod I8 passes. A resilient means such as a spring 81 is disposed in each of housings 8| and 82, each spring acting to pull the respective cam and paddle in the direction of rotation and against the resistance of lime so as to cause either paddle to movein the direction of rotation and thereby-cause rods I1 and 18 to be lowered when the lime level has fallen sufliciently below either paddle.

Housings 8| and 82 are connected by a hollow shaft 88 through which rod I8 passes; a lower shaft 51', to which hbusing 82 and collar 62 are attached, is journalled in well in a manner similar to that previously described; and arms 03' are attached at one end to hollow shaft 88 adjacent housing 8| and at the other end to scraper BI. Housings M and 82, as well as hollow shaft 88, are filled with a suitable lubricating medium, such as oil, the lubricant also permeating between push rods l1 and I8 and hollow shaft 31' and acting also as a gas seal. For sealing purposes, stub shafts 84 and 85 are each provided with a'packing gland 38', While hollow rod 11 and hollow shaft 31' are provided at their upper ends with packing glands 39 and 89, re-

spectively.

A disk 9! is secured to the upper end of push rod 10, the disk engaging one end of a lever 92; and the opposite end of lever 92 is connected by a cable 93 with the operating arm of a lower level switch 99. A disk 95 is similarly secured to the upper end of hollow push rod 11, disk 95 engaging one end of a lever 96 and the opposite end of the lever being-connected by a cable 91 with the operating arm of an upper level switch 98. Hand pull rings 98' and 48" are connected by suitable cables to the ends of levers 92 and 95, respectively, for operating the switches manually, if desired.

An electrical circuit, as in Fig. 5, which acts in conjunction with the switches 94 and 98 in controlling'the motor driving the helicoid screw 26, includes a three phase switch operated by a relay I0l. One side of the winding of relay IN is connected through a resistance I02 to one phase of the line supplying current to winding I03 of a three phase A. C. conveyor driving motor, and they other side of the relay is connected by a common wire wt to one side of each of switches 99 and 98. The-other side of lower level switch 94 is connected by a line I05, which includesv a secondary control switch operated by relay It". to a second phase of the supply-line; and the other side of upper level switch 98 is connected by a wire H09 to the second phase of the supplyline. The switch 99 will always be closed when the height of lime within the hopper is above the lower level L, since, due to the resistance of the lime, lower paddle it will lag backwardly against the tension of spring 87, and push rod 79 will be forced upwardly to rock lever 92, thereby closing switch 99. However, closing of switch 94 will not start the driving motor since the switch in line I05 will be open until relay IdI operates. When lime reaches the upper level U. the resistance to rotation of upper paddle '35 will cause the upper paddle to lag backwardly from its normal position against the tension of spring 9? and push hollow rod Ill upwardly, thereby rocking lever 96 and closing switch 98.

When switch 98 is closed, the starting circuit through relay lfil will be completed, and the three phase switch controlling the driving motor will be closed, as well as the switch in line I05.

When the level of lime drops below the upper level U and switch 98 is opened, the driving motor will still operate, since both switch and.

the switch in line I05 will remain closed, the relay IOI acting as a holding relay. However, when thelevel of lime drops to the lower level L, sumcient resistance to the rotation of lower paddle I5 will no longer be offered by the lime,

switch 94 will be opened, relay II)! will no longer be energized, and the three phase switch controlling the winding I03 as well as the switch in line I05 will drop open, thereby stopping the driving motor. When lime again builds up within the hopper above the lower level L and offers suflicient resistance to rotation of paddle 16 to displace the paddle from its normal position, switch 94 will be closed, but will not start the driving motor since the switch in line I05 will still be open. But when the level of lime again reaches the upper level U, switch 98 will be closed, again energizing relay IN, and the driving motor will againbe started. The removal of lime will continue in this manner, the level of lime within the hopper always being maintained between predetermined lower and upper levels. Obviously, a D. C. driving motor may be used,

but the essential elements of the control circuit will remain the same, line wire I01 and its corresponding phase switch being omitted.

The embodiment of the invention illustrated in Fig. 6 is similar in many respects to the two embodiments of the invention just described, a shaft assembly A" including a hollow shaft 31" extending downwardly to the bottom of the hopper and journalled in ,well 60 in a manner similar to that previously described. Arms 63", similar to arms.63 and B3 of Figs. 1 and 3, and scrapepiil are attached to the hollow shaft. The assembly A is rotated at a relatively slow speed by suitable means (not shown, but preferably similar to the rotating means of the two modifications just described), and lime is removed from outlet 25 of hopper H by suitable conviaying means, preferably similar to that of Fig.

In the assembly A", a fixed arm II I is keyed to hollow shaft 31" adjacent the lower end thereof, and a floating arm I I2 is Journalled on shaft 31" adjacent the upper level U. The floating arm II2 ismotated by fixed lower arm III through springs M3, the resistance of lime to rotation of springs H3 and floating arm II2 effecting a change in the angular relationship between floating arm H2 and hollow shaft 31". A cable II4, attached to one end of fixed arm III and passing through a suitable hole in the corresponding end of floating arm H2 and thence into the shaft 31", operates a suitable snap-action switch, preferably similar to switch 45 of Fig. 1, for controlling the dfiving motor for the lime removal conveyor. Cable I I4 and hollow shaft 31" preferably pass through suitable stuffing boxes in a manner similar to that of the previous modifications.

. Cable H4 and the snap-action switch are preferably so correlated that when the height of lime has reached upper level U, the resistance of lime to rotation of floating arm II2 will cause a change in the angular relationship between floating arm H2 and both shaft 31" and fixed arm III suificient to shorten the effective length of cable II4, thereby closing the switch to start the conveyor driving motor. In addition, the snap-action switch may be so connected with cable I I4 that when the level of lime has dropped to the lower level L, the resistance thereof to rotation of springs II3 will exert a suificiently less pull on cable II4 to cause the switch to snap open, thereby stopping the conveyor driving motor.

In the embodiment of the invention illustrated in Figs. 7-9, a paddle or stirrer I2I is rotated about a horizontal axis, a horizontal shaft I22 passing through a stufilng box S into a hopper H. In this embodiment, the lower level of lime may be maintained at a higher predetermined position, if desired, in order to provide a more effective seal. Resistance to rotation of stirrer I2I will cause a change in the angular relationship between the stirrer and a hollow drive shaft I23, and also between the two halves of a spring loaded coupling P. This movement of the two halves of the coupling relative to each other will exert a pull on a cable I24 attached todriven half I25 of coupling P and passing through driving half I26 of coupling P and also through hollow shaft I23. Cable I24 is attached to swivel joint I21, which permits relative rotation of cable I24 with respect to a cable I28. A pull on cable I24 will be transmitted through the swivel joint and cable I28 to a lever I29, the opposite end of which is attached to operating arm 44 of snapaction switch 45 controlling the conveyor driving motor. Hollow shaft I23 is driven by a motor M" through a reduction pinion I30 and a gear I3I keyed to shaft I23.

The control apparatus of Fig. 7 operates in substantially the same manner as that of Fig. 1, and the lengths of cables I24 and I28 are prefer ably so proportioned that at any predetermined upper height of lime within the hopper H, 'such as upper level U, resistance to rotation of paddle I2I will cause switch 45 to snap closed and start the conveyor driving motor, while at any predetermined lower height of lime within the hopper, such as lower level L, reduced resistance to rotation of paddle I2I will cause switch 45 to snap open and stop the conveyor driving motor.

The coupling P, as in' Fig. 8, comprises a female or driven half I25 keyed to shaft I22 and provided with a groove or recess I32 and a pair of opposltely disposed pins I33.- Male or driving half I26 of coupling P is keyed to shaft I23, and is provided with oppositely-disposed pins I36 which extend into recess I32 in the female half when the coupling is assembled. Disposed between each set of pins isa coil spring I36, which transmits rotation of shaft I23 to shaft I22, but permits the male and female halves of the coupling to twist relative to each other upon the interception of lime by stirrer I2I and resistance to rotation thereof. Cable I24 is fastened to an ear 131 on the female half of the coupling, and passes through a suitable hole I38 in a similar ear I39 on the male half of the coupling. When resistance to rotation of paddle I2I is offered by the lime and the two halves of the coupling twist relative to each other, a pull will be exerted on cable I24 due to a displacement of ear I39 with respect to ear I31.

The novel stuffing box assembly S, as in Fig. 9, includes a shell I4I secured in a suitable aperture in the side of the hopper H in a suitable manner, such as by welding. A bushing I42, made of cast iron or other suitable long-wearing bear-- ing material, is pressed into shell I4I to provide a bearing for an enlarged end I43 of shaft I22, the enlarged end terminating at a shoulder I44. Bushing I42 may be lubricated by means of a standard grease cup connection I45, and grease is retained between the bearing surfaces by a felt washer I46 bearing against shoulder I44 and a pair of felt washers I41 bearing against the ends of shell MI and bushing I 42. Washer I46 is resiliently held against shoulder I44 by a spring I48 acting between a steel washer I48 and a stufiing box nut I50, which is threadedly secured to shell I4I outside the hopper and by means of which the tension of spring I48 may be adjusted. Washers I41 are held in contact with the end of the shell and bushing and are also forced against the shaft by a cap I5I, which is held in position and resiliently forced against washers I41 by springs I52 secured to the inner wall of the hopper and to ears I53 formed on cap I5I.

This novel stufling box not only provides a bearing for the shaft, but also prevents an outflow of acetylene or an inflow of air, since grease filling the machined clearancebetween the shaft and bushing I42 also tends to saturate washers I46 and I41, thereby providing an effective seal against any passage of gas.

In the modifications of the control apparatus illustrated in Figs. 10 and 11, control of the conveyor driving motor is effected electrically, and these modifications are particularly applicable to the apparatus illustrated in Fig. '7, the electrical circuit and parts shown being substituted for coupling P and parts associated therewith. However, these modifications may be utilized in other instances in which a paddle or scraping means is rotated within the lime hopper, such as the scraper 6| of Fig. 1 or Fig. 3. The modification illustrated in Fig. 10 is adapted to be utilized in connection with a D. C. motor driving a paddle or scraper within the hopper, while the modification illustrated in Fig. 11 is adapted to be utilized in connection with an A. C. motor.

When the driving means for the paddle or scraper within the hopper is a D. C. motor I6I, as in Fig. 10, current is supplied thereto from a line I62, and a solenoid I64 is connected in series with the motor by wires I65. When resistance of lime to rotation of the paddle or scraper within the hopper has increased to a predetermined extent, thereby increasing the current 2,277,879 drawn by the paddle or scraper motor, the curswitch relay l! which controls the conveyor driving motor, such as in a manner similar to that of'the relay I! of Fig. 5. When switch E68 closes, relay ml will become energized, thereby starting the motor driving the lime removal conveyor. When current drawn by motor ltl decreases due to the falling of the lime-to a lower predetermined level, the current passing through solenoid I66 will also decrease, and the pull of spring it? will be sufficient to open switch I68, thereby opening the circuit through relay NH and shutting off the motor driving the lime removal conveyor. The pull of solenoid 66d and tension of spring l 61 may be so correlated that the lime removal conveyor motor will be started and stopped when lime within the hopper reaches any predetermined upper and lower levels, respectively, merely by adjusting the tension of spring l6? and the number of turns insolenoid 966. tained in a number of different ways.

When the motor driving'the paddle or scraper within the hopper is an A. C. motor l'll as in Fig. 11, a bimetallic strip, I72 is connected in series with one phase of line I13 supplying the motor I, through wires lid. An increase in the current flowing through the field windings of motor I, due to a greater resistance of lime to the movement of a paddle or scraper within the hopper, will cause a greater flow of current through the bimetallic. strip. A greater flow of current through strip I12 will cause the strip to become heated and bend downwardly, due to the differential expansion of its metallic parts. This will operate to close contacts H5, which are interposed on one side of a line Ill supplying current to switch relay "H" which controls the motor driving the lime removal conveyor, as before. When strip I 72 becomes heated and closes the contacts I15, the lime removal conveyor motor will be started, and when the resistance to rotation of the paddle or scraper by the lime has decreased to a sufficient extent, due

to fall of the lime to a lower predetermined level, a lesser amount of current will be drayvn by motor Ill and a correspondingly lesser amount of current will flow through strip H2. The smaller flow of current through strip 512 will cause the heating effect in strip I12 to decrease, and strip I12 will bend upwardly again to open contacts I15, thereby stopping the motor driving the lime removal conveyor. The contact 615 carried by the bimetallic strip H2 is preferably insulated therefrom by suitable means, such as rubber. Obviously, a suitable thermostatic switch of any other type may be substituted'for the bimetallic strip I12.

It will be understood that the principles of Obviously, such adjustment may be obor container will be effected in substantially the same manner as previously described. Other changes may be made without departing from the spirit and scope of this invention.

What is claimed is:

1. In apparatus for maintaining the level of finely divided material in a container within predetermined upper and lower limits, the combination comprising a motor driven conveyor for conveying such finely divided material between the interior of saidcontainer and a point outside thereof; control means for the conveyor motor; at least one element mounted within said container and movable through a predetermined circular path in the container; a shaft; means for. rotating said shaft; means operatively connecting said shaft to said element to rotate said element through such predetermined circular path in the container, said means beingoperative to provide for a lag in the rotation of said element with respect to said shaft due to resistance of material in said container to movement of said element when material in said container reaches a predetermined level; and means operative in response to suclilag in the rotation of said element to actuate said control means.

2. In apparatus as claimed in claim 1, resilient means tending to resist a lag in the rotation of said element with respect to said shaft, the resistance of the material to rotation of said element overcoming the force of said resilient means thereby to cause such lag in the rotation of said element.

3. In apparatus for maintaining the level of finely divided material in a container within predetermined upper and lower limits, the combination comprising a, motor driven conveyor for conveying such finely divided material between the interior of said container and a point outside thereof; a single element rotatably mounted in said container; a shaft; means for rotating said shaft; means operatively connecting said shaft to said element, said means being operative to provide for changes in the angular relation of said element to said shaft due to the resistance offered by-said material to movement of said element; control means operative in response to a predetermined angular relation of said element to said shaft when said material reaches a predetermined upper level in said container, to start the conveyor motor; said control means also being operative, in response to another predetermined angular relation of said element to said shaft when said material reaches a predetermined lower level in said container, to stop the conveyor motor.

4. Apparatus for controlling the level of finely divided material within a. container, comprising means for conveying such finely divided material between the interior of said container and a point outside thereof; a rotatable shaft extending into said container; means for rotating said shaft; a

paddle disposed within said container and rothis invention may be applied to apparatus for tated by said shaft, said mounted at a longitudinally fixed point on said shaft, and being so arranged that a rise in the level of such material within said container will cause achange in the angular relationship of said paddle with respect to said shaft; and means actuated upon such change in angular relationship for controlling said conveying means.

5. In apparatus for maintaining the level of finely divided material in a container within predetermined upper and lower limits, the combinapaddle being pivotally' paddle in its normal tion comprising a motor driven conveyor for conveying such finely divided material between the interior of said container and a point outside to provide for a change in the angular relation of'said paddle to said shaft due to the resistance offered by said material to movement of said path; and means operative in response to such change in the angular relation of said paddle to said shaft to actuate said conveyor motor control means.

6. In apparatus as claimed in claim 5, force imposing means tending to resist a change in the angular relation of said paddle to said shaft.

'7. Apparatus for controlling the level of finely divided material within a container, comprising means for conveying such finely divided material between the interior of said container and a point outside thereof; a pivoted paddle disposed within said container; means including a hollow shaft for rotating said paddle within said container; a rod movable within said hollow shaft and operably connected with said paddle so as to be actuated in accordance with variations in the level of material within said container, such variations causing said paddle to-pivot; and means actuated by said rod for controlling the operation of said conveying means.

8. Apparatus as defined in claim '7, in which said paddle is pivoted about an axis substantially perpendicular to theaxis of said hollow shaft.

9. Apparatus as defined in claim 7, in which said paddle is pivoted about an axis substantially parallel to the axis of said hollow shaft.

10. Apparatus for controlling the level of finely divided lime hydrate in the lime hopper of an acetylene generator, comprising means for removing such lime from said hopper; a hollow shaft extending into said hopper; a housing secured to and rotatable with said shaft within said, hopper; a push rod movable longitudinally within said shaft; a paddle disposed within said hopper and mounted on a stub shaft carried by said housing; means for rotating said hollow shaft; means for moving said rod longitudinally of said hollow shaft when said paddle is caused to pivot about the axis of said stub shaft due 'to a change of the level of lime within said hopper; and means actuated by movement of such rod for controlling said removing means.

11. Apparatus as defined in claim 10, in which said housing is filled with a sealing and lubricating medium.

12. Apparatus for controlling the discharge of finely divided lime hydrate from the lime hopper of an acetylene generator, comprising means for removing accumulated lime from the outlet of said hopper; a hollow shaft extending verti-' cally into said hopper; a push rod movable within said hollow shaft; a relatively broad flat paddle disposed within said hopper and pivoted about a substantially horizontal axis, said paddle being rotatable with said hollow shaft; means for rotating said hollow shaft; means operatively connecting said paddle and said push rod for moving said push rod upwardly and downwardly in response to upward and downward pivotal movement of said paddle caused by a rise or fall of the level of lime within said hopper; and means actuated by movement of said push rod for controlling said removing means.

13. Apparatus for controlling the discharge of finely divided lime hydrate from the lime hopper of an acetylene generator, comprising means for removing accumulated lime from the outlet of said hopper; a hollow vertical shaft extending into said hopper; means for rotating said shaft; a hollow push rod movable vertically within said hollow shaft; a second push rod movable vertically within said hollow push rod; a paddle disposed within said hopper and rotatable with said hollow shaft at an upper predetermined level in said hopper; a second paddle disposed within said hopper and rotatable with said hollow shaft at a lower predetermined level in said hopper; cams engaging the lower end of each of said push rods; means operatively connecting said paddles with said cams; resilient means for urging each of said paddles in the direction of rotation whereby either of said paddles will tend to lag due to an interception of lime by said paddles and such lag will cause said cams to move said push rods within said hollow shaft; and means actuated by movement of said push rods for controlling the operation of said removing means.

14. In apparatus for controlling the level of finely divided material within a container, the combination of means for conveying such material between the interior of said container and a point outside thereof; a hollow vertical shaft extending into said container; means for rotating said shaft; a lower paddle secured to said shaft and rotatable therewith; an upper fioating paddle pivoted on said shaft; resilient means connecting said lower paddle and said upper paddle for rotating said upper paddle along with said lower paddle, said upper paddle tending to la behind its normal rotation when material wi hin said container rises in level to resist rotation of said upper paddle; and a cable attached to said lower paddle and passing through one end of said upper paddle and thence into said hollow shaft whereby such a lag in the rotation of said upper paddle will tend to shorten the effective length of said cable CHARLES NESS. HUGO V. KOJOLA. GUY A. DUNN. 

